Electromagnet cuffs

[The inspector]

I’ll make something myself for this session! You never know for future ones though! I’ll keep you in mind!

[ltxrob]

A similar relay, but 3 times cheaper and a bit smaller in size.

Yes. I saw those too. But they start timing on power on and can be turned off again by powering off eg a switch. 

The one I ordered has the option of one time start trigger irrelevant of time of power being connected

[ltxrob]

My idea was to connect a battery directly to the magnet. Similar to icelocks - battery discharged - you are free. The approximate lock-time can be calculated.

That was my plan too. But I decided I wanted to be able to set it less than approx 1hr if I wanted too. 
This will still be the fail safe as 2 x 9v batteries in series will give me 18v giving a stronger hold and the electronics will run from it too. When they run out everything will fail safe. 
So even if I chose 15-30 mins.... I’d still be free in 1 hr if something broke.

[BoundWolf]

I wish I had a 3D printer. Need to make some surrounds for my mag locks. 60kg rated.

If you have the file, you can send it to Shapeways (or a similar service) - they'll print out the parts and send it to you.

[The inspector]

That is useful to know! Thanks for that! Didn’t realise there were mail order 3D printers!

[Like Ra]

2 x 9v batteries in series will give me 18v giving a stronger hold

The magnets can overheat and painfully burn. Been there. I prefer to power a 12v magnet with no more, than 9v.

[ltxrob]

2 x 9v batteries in series will give me 18v giving a stronger hold

The magnets can overheat and painfully burn. Been there. I prefer to power a 12v magnet with no more, than 9v.

Yes it was something I was going to check. 
If they do run hot I’ll put a 7812 or 7809 voltage regulator in and  run them like that. 
Board runs between 16  & 30v  so need to have 18v available.

[ltxrob]

Yes 18v for 10 minutes made the magnets get quite hot.
7809 & 7812 regulators ordered.
Will test again on 12v to see if they get hot too.

[ltxrob]

Ok tested further with 12v and 9v

Ran them both for 10-15 mins each

Neither got as hot as 18v but 12v was still a little warmer than 9v

Should not be an issue with my 3D prints going soft, I’d estimate temperature to have reached 45-50 deg C, while the 18v was probably close to 75 deg and hard to hold.

[Like Ra]

I had 24V electromagnetic cuffs. Had to run them on 12V.